I had a friend with a BluRay drive extract the audio from my copy of a concert BluRay disc into AC3 files which he returned to me, but now I'm not sure what the best way would be to convert those AC3 files into AAC files.

I've read that it's not possible to go directly from AC3->AAC, but instead have to use WAV as an intermediary; AC3->WAV->AAC. I can probably figure out how to do this, but why should I be the one to make two steps? Is there software already available (free preferred, but not required) that will simply let me plug in an AC3 file and get an AAC equivalent out?

When I say AAC equivalent, that means identical channel setup to the source AC3 files by default, but perhaps also preferences to constrain it to 2 channel or anything else I'd like.

6 Answers
6

VideoLAN can do this. Select "Streaming/Transcoding Wizard" from the File menu. Choose "Transcode/Save to file". On the next page click "Choose" and open your AC3 file. On the next page tick "Transcode audio" and choose "MPEG 4 Audio" and choose the desired bitrate. Click "Next", choose "MPEG 4 / MP4", click "Next" again and "Choose..." where to save the file. "Next" and "Finish".

The file VideoLAN creates has the extension .mp4, change it to .m4a and there you go.

I tried this as part of my testing yesterday and it didn't work–no file was created. I'll give it another go.
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jabergFeb 23 '12 at 22:40

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And today it works…via a remote screen login from my iPad no less. Not sure what changed, but this looks like the solution.
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jabergFeb 23 '12 at 22:49

It does work, but the quality is ghastly. I'm not sure what exactly is wrong, but the end result is not nearly as good as I'd prefer. Ghastly = this really obnoxious "warble" in the low end hits.
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Jason SalazFeb 24 '12 at 2:26

I'm awarding you the bounty because this is certainly the best result so far. But I still have more specific problems which I think I will open up another question for.
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Jason SalazFeb 28 '12 at 4:33

Thanks, I'm still trying to get a something better...
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Max RiedFeb 28 '12 at 9:25

I was playing with this problem today and while I didn't find a batch process solution, I did learn something that may me useful to others faced with this problem.

If you install the Perian QuickTime components, QuickTime Player X will open and play AC3 files. Unfortunately, it will not export them. However, if you use QuickTime Player 7 Pro (again, with Perian installed) you can export an AC3 file into an AIFF or WAV format. Once you have the file saved in one of those formats, it is trivial to create an Automator Droplet (or service) to convert the files into an AAC/MP4 format.

Would using Automator to run Apple- or shell-scripts that call ffmpeg be a workable solution? This site has some ideas on AC3 to MP3 using ffmpeg. The first comment mentions this which seems pretty close:

(1) Handbrake doesn't work with audio only files, as I've recently learned. (2) Handbrake could work with video files with ac3 as the source audio. Perhaps I could have the BRay re-ripped as video files, I could convert using Handbrake, and then extract the AAC audio from the m4v. Those source video files are going to be huge though.
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Jason SalazFeb 22 '12 at 0:15

What about ffmpeg and a script? (See edit.)
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CajunLukeFeb 22 '12 at 0:56

I realize that your post is kind of a mash of edits now CajunLuke, but your current second paragraph is probably almost perfect. Note that your command is very similar to the one I linked in my first comment. I really need to get used to considering ffmpeg more quickly.
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Jason SalazFeb 22 '12 at 2:32

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@Jason I excised the Handbrake part and stuck to Automator and ffmpeg.
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CajunLukeFeb 22 '12 at 15:14

I downloaded Audio Converter and tested it. The file it produced was at a low bitrate, and there doesn't seem to be a way to change that (at least in the free version.) Also, the file it created wouldn't play via QuickLook and only showed a subset of Applications available for Open with…. QT X wouldn't recognize the file in its open file requester.
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jabergFeb 22 '12 at 21:52